Brake fluid



Patented May 9, 1950 BRAKE FLUID George L. Doelling, St. Louis, Mo.,assignor to Wagner Electric Corporation, St. Louis, Mo., a

corporation of Delaware No Drawing. Application January 19, 1948,

Serial No. 3,162

8 Claims.

' This invention relates to brake fluids and its object is to provide abrake fluid that utilizes available synthetic products in place ofnatural products, such as castor oil, in forming the fluid, which fluidswill have the same or improved properties as those possessed by priorfluids and which will be lower in cost.

Hydraulic brake fluids, as manufactured and sold in the past, consistedchiefly of an oil or lubricant to provide the required amount oflubrication, and a diluent, usually of low viscosity, to give therequired fluidity at low temperatures. One such fluid containsapproximately 50% by volume of diacetone alcohol and 50% by volume ofcastor oil, or mixtures of castor oil and ethyl alcohol or castor oiland other solvents. Ricinoleate esters. better than castor oil, alsohave been used along with a diluent. These fluids,

- consist chiefly of an oil and a diluent, and have certaindisadvantages. They usually have a fairly high oil content varying from30 to 50%, which makes them very costly. The high oil-content fluidstend to have a rather high viscosity at -30 F. or lower, and if castoroil is used, they actually freeze at low temperatures. If the diluentcontent is raised too high, then the rubber-swelling effect becomes toogreat for satisfactory use in brakes.

The improved fluid of the instant invention contains several ingredientswhose proportions with reference to the total volume of the fluid areheld within rather narrow limits. One of these ingredients, monoordi-ricinoleate of an ethylene, propylene or butylene glycol constitutingfrom to 25% by volume of the fluid is employable as a lubricant. Thediluent, which is another ingredient, is preferably from 45% to 70% byvolume of the fluid of one of the group consisting of the propylalcohols, the butyl alcohols, the arnyl alcohols, methoxy-methoxyethanol, and the lower mono-alkyl ethers of ethylene glycol, diethyleneglycol, propylene glycol and dipropylene glycol. Another ingredient iscom- ..bined with this aforementioned oil and diluent,

which is an aliphatic glycol having from 2 to 4 carbon atoms permolecule, inclusive, and varies between 3%-15% by volume of the totalvolume .of fluid. Another ingredient is 2-methyl-2, 4

'pentane diol, which varies from 10% to 24% of the volume of the fluid.It is generally desirable to add a small but eflective amount ofcorrosion inhibitor to this fluid, which may be material such aspotassium ricinoleate.

Y The glycol ricinoleate in this new composition has the function ofproviding the proper amount 2 of lubrication. If too low a percentage ofoil is used, the fluid will be lacking in lubricating qualities and ifmore than about 25% of this oil is used in this composition theviscosity at low winter temperatures becomes high. The small amount ofaliphatic glycol used has the property of reducing the adverse ordeteriorating effect on rubber. If less than about 3% is used, this willnot be satisfactorily accomplished, but if more than about 15% is used,then the hydroscopic and corrosive properties of these glycols tend togive the finished fiuid undesirable properties. The 2- methyl-2.4-pentane diol acts partially as a replacement for oil, due to itsconsiderable viscosity, and it also acts as a coupling agent, to improvethe solubility of the oil in the diluent at low temperatures. If morethan about 20 to 24% is used, this, plus the oil present, will give thefluid an undesirably high viscosity at low winter temperatures. The 45%to of diluent used serves to give the fluid an operable viscosity at alloperating temperatures. If too high a percentage of diluent is used, thelubricating value of the fluid is too low, and the adverse ordeteriorating effect on rubber is increased, and if less than about 45%of diluent is used, the fluid will not operate eiliciently under extremelow temperature conditions. Besides the compounds above mentioned, otherorganic solvents, having a boiling point of about C. or higher, andwhich are relatively inert to rubber and metals, and have a 10w freezingpoint, can be used as the diluent. Suitable corrosion inhibitors includepotassium, sodium or other alkali-metal salts of castor oil or otherfatt acids, amine-phosphates, nitrites, borates and otherbufiermaterials. The amount of corrosion inhibitor I prefer to use isfrom about 0.2% to about 3.0% of the finished fluid by weight.

Examples of the new composition in which the percentages given are onlyapproximate are as follows:

Example 1 Per cent by volume Propylene glycol mono-ricinoleate about 1'7Propylene glycol about 6 2-methyl-2, 4-pentane diol about 15 Isobutanolabout 62 A corrosion inhibitor comprising potassium ricinoleate wasadded to a fluid of the above composition at the rate of about 1.9 gramsper cubic centimeters of the fluid. This fluid had a boiling point of241 F. and in a cold test remained readily fluid after five days at ,40F. The speciflc gravity at 20/2 0 C. is 0.8714 and the viscosity at 100F. is 50 seconds Saybolt, and at -40 F. is 3900 seconds Saybolt. A 1%;inch rubber sea-ling cup immersed in this fluid for five days at 70 C.gained only 6.7% in weight.

This fluid was tested as to lubrication by a stroking test and after150,000 strokes there was very little wear on the cylinders or pistons,in the wheel cylinders and master cylinder, and the rubber parts of thebraking system were in good condition. Corrosion tests run on this fluidfor 120 hours at 210 F. against the metals usually present in the brakesystem, namely, tinplated steel, steel, aluminum, cast-iron, brass andcopper gave losses in weight ofthemetal in each case from zero to a fewtenths of a milligram per square centimeter ofzexposed surface.

The tests in the brake systems of a number of automobiles under winterand summer .conditions have shown that this is an operative "hydraulicbrake fluid.

Example .2

Per .centby volume .liropylene glycol mono-ricinoleate about 15Propylene glycol about 5.5 2-.methyl2, 4-pentane'diol -about.17.5-Isobutanol about 62 A corrosion inhibitor comprising potassium"ricindleate was added to the above fluid at the 'rateoi about 1.9 gramsper cc. of the fluid. This fluid had properties very much like the fluidin Example 1. It "had aboiling point of '243" F. and

"viscosity at 100 F. of 51 seconds Saybolt, and

at -40 F. of 3480 seconds Saybolt. The'lubri- "cation, corrosion, effecton rubber'and other tests all indicated that this fluid is operablein"hydraulic brake systems.

Example 3 Per cent 'by yolume Propylene glycol mono-'ricinoleate about23 Propylene glycol about 5 2-fmethyl-2, i-pentanediol about 16Methoxy-methoxy ethanol about 56 Example 4 Per cent by volume Ethyleneglycol mono-riclnoleate about25 Ethylene glycol about "7 2-methyl-2,e-pentane diol about 20 'Mono-butyl ether of ethylene glycol about 48Diamylamine as a corrosion inhibitor was added to a fluid -:of the abovecomposition at the rate .of 0.75 %.v by volume and 85% phosphoric acidat the rate of 0.125% by volume of the fluid.

After mixing, this fluid had a specific gravity at 'I20?/20 C. of 0.940and a boiling'point of 330 F. .After four days at i0F. the mixturewasreadily fluid and'in the other tests was found to be operable asabrake fluid.

A corrosion inhibitor comprising sodium ricinoleate was added to a fluidof the above composition at the rate of 0.4 gram per cc. of the fluid.After solution, this fluid had a clear straw-color and a specificgravity of 0.935 at 20 C. After three days at =l0 F. it was readilyfluid and the other testson'it indicated that it was operable as a brakefluid.

Example 6 Per cent by volume 1,3 butylene glycol mono-ricinoleate about11 1,3 butylene glycol about 10 2-rmethyl-.2, 4-pentane diol about 10.Mono-ethyl ether of diethylene glycol about 69 Example 7 Per cent byvolume Propylene glycol mono-ricinoleate about/l5 Propylene glycol about15 2-methyl-2, 4-pentane diol about 10 Mono-ethyl ether of ell-propylene.gly-

col about 60 A corrosion inhibitor comprising potassium ricinol'eate wasadded to a fluid of the above composition atthe 'rate of 1 gram per 1-00cc. of fluid. After mixing, this fluid had -a boiling point of 329.5 anda specific gravity aOf 20720 C. of ;953. After three days'at 40 in 'the'cold test this fiuidwas clear, readily fluid and fairly low inviscosity, and is "operable as a. brake fluid.

Example 8 Per cent by volume Propylene glycol mono-ricinoleate about20Propylene glycol about 8 2-methyl-2, 4-pentane diol about 1'5 "Butanol(normal) about 57 A corrosion inhibitor comprising potassium.ricinoleate was added to :a fluid of the above composition at the rateof 1 gram per 100 .cc. of fluid. After mixing, this fluid had a boilingpoint of 249 F. and a specific gravity of 209/20" C. of 0.882. In thecold test, after 3 days at -40 the fluid was clear and readily fluid,and in other tests this fluid was shown toeb operable as a brake fluid.

Example .9

Per cent by volume Propylene glycol mono-ricinoleate about 217:5

A corrosion inhibitor comprising potassium rlcinoleate was added to'afluid of the above composition at the rate of 1 gram per 100 cc. or thefluid. After mixing these materials a clear. strawcolored liquidresulted having a specific gravity of 0.877? at 20/20 C. After beingheld at 40 F. for three days, this fluid was very readily fluid andapparently operative as a brakefluid.

What I claim is:

1. An operating fluid for pressure apparatus "comprising per 100 partsby volume, from 10 to 'Qliparts by'volume of 'a lubricant selected fromthe group consisting of the monoand diricinoleates of the aliphaticglycols having the formula HOCnH2n-OH, in which n is an integer from 2to 4, inclusive, from 3 to 15 parts by volume of an aliphatic glycolhaving the formula HO-CnH2n-OH, in which n is an integer from 2 to 4,inclusive, from to 24 parts by volume of 2-methyl-2, 4-pentane diol,from 45 to 70 parts by volume of a diluent selected from the groupconsisting of the propyl alcohols, the butyl alcohols, the amylalcohols, methoxy-methoxy ethanol, and the lower mono-alkyl ethers ofethylene glycol, diethylene glycol, propylene glycol and di-propyleneglycol, and a small but effective amount of corrosion inhibitor.

2. An operating fluid for pressure apparatus comprising per 100 parts byvolume, from 10 to 25 parts by volume of butylene glycolmonoricinoleate, from 3 to parts by Volume of butylene glycol, from 10to 24 parts by volume of 2-methyl-2, 4-pentane diol, from 45 to '70parts by volume of a diluent selected from the group consisting of thepropyl alcohols, the butyl alcohols, the amyl alcohols, methoxy-methoxyethanol, and the lower mono-alkyl ethers of ethylene glycol, diethyleneglycol, propylene glycol and dipropylene glycol, and a small buteffective amount of a corrosion inhibitor.

3. An operating fluid for pressure apparatus comprising per 100 parts byvolume, from 10 to parts by volume of a lubricant selected from thegroup consisting of the monoand cli-ricinoleates of the aliphaticglycols having the formula HO-CnH2nOI-I, in which n is an integer from 2to 4, inclusive, from 3 to 15 parts by volume of an aliphatic glycolhaving the formula HOCnH2nOH, in which n is an integer from 2 to 4,inclusive, from 10 to 24 parts by volume of 2-methyl-2, 4-pentane diol,from to '70 parts by volume of an alcohol having the formula C4H9OH, anda small but effective amount of a corrosion inhibitor.

4. An operating fluid for pressure apparatus comprising per 100 parts byvolume, from 10 to 25 parts by volume of propylene glycolmonoricinoleate, from 3 to 15 parts by volume of propylene glycol, from10 to 24 parts by volume of 2-methyl-2, 4-pentane diol, from 45 to partsby volume of a diluent selected from the group consisting of the propylalcohols, the butyl alcohols, the amyl alcohols, methoxy-methoxyethanol, and the lower mono-alkyl ethers of ethylene glycol, diethyleneglycol, propylene glycol and dipropylene glycol, and a small buteffective amount of a corrosion inhibitor.

5. An operating fluid for pressure apparatus comprising per parts byvolume, from 10 to 25 parts by volume of propylene glycolmonoricinoleate, from 3 to 15 parts by volume of propylene glycol, from10 to 24 parts by volume of 2-methyl-2, 4-pentane diol, from 45 to 70parts by volume of an alcohol having the formula C4H9OH, and a small butefiective amount of a corrosion inhibitor.

6. An operating fluid for pressure apparatus comprising per 100 parts byvolume, from 16 to 25 parts by volume of propylene glycolmonoricinoleate, from 3 to 15 parts by volume of propylene glycol, from10 to 24 parts by volume of 2-methyl-2, 4-pentane diol, from 45 to 70parts by volume of methoxy-methoxy ethanol, and a small but efiectiveamount of a corrosion inhibitor.

7. An operating fluid for pressure apparatus comprising per 100 parts byvolume, from 10 to 25 parts by volume of propylene glycolmonoricinoleate, from 3 to 15 parts by volume of propylene glycol, from10 to 24 parts by volume of 2-methyl-2, 4-pentane diol, from 45 to '70parts by volume of isobutanol, and a small but effective amount of acorrosion inhibitor.

8. An operating fluid for pressure apparatus comprising per 100 parts byvolume, from 10 to 25 parts by volume of propylene glycol mono--ricinoleate, from 3 to 15 parts by volume of propylene glycol, from 10to 24 parts by volume of 2-methyl-2, 4-pentane diol, from 45 to 70 partsby volume of the ethyl ether of ethylene glycol, and a small buteifective amount of a corrosion inhibitor.

GEORGE L. DOELLING.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,226,487 Zink Dec. 24, 19402,232,581 Woodhouse et a1. Feb. 18, 1941 2,305,228 Woodhouse et al. Dec.15, 1942 2,337,650 Dolian Dec. 28, 1943

1. AN OPERATING FLUID FOR PRESSURE APPARATUS COMPRISING PER 100 PARTS BYVOLUME, FROM 10 TO 25 PARTS BY VOLUME OF A LUBRICANT SELECTED FROM THEGROUP CONSIST5ING OF THE MONO- AND DI-RICINOLEATES OF THE ALIPHATICGLYCOLS HAVING THE FORMULA HO-CNH2N-OH, IN WHICH N IS AN INTEGER FROM 2TO 4, INCLUSIVE, FROM 3 TO 15 PARTS BY VOLUME OF AN ALIPHATIC GLYCOLHAVING THE FORMULA HO-CAH2N-OH, IN WHICH N IS AN INTEGER FROM 2 TO 4,INCLUSIVE, FROM 10 TO 24 PARTS BY VOLUME OF 2-METHYL-2, 4-PENTANE DIOL,FROM 45 TO 70 PARTS BY VOLUME OF A DILUENT SELECTED FROM THE GROUPCONSISTING OF THE PROPYL ALCOHOLS, THE BUTYL ALCOHOLS, THE AMYLALCOHOLS,, METHOXY-METHOXY ETHANOL, AND THE LOWER MONO-ALKYL ETHERS OFETHYLENE GLYCOL, DIETHYLENE GLYCOL, PROPYLENE GLYCOL AND DI-PROPYLENEGLYCOL, AND A SMALL BUT EFFECTIVE AMOUNT OF CORROSION INHIBITOR.